1. Field of the Invention
The present invention relates to a magnetron for generating radio frequency outputs, and more particularly to a coupling device for an antenna feeder in such a magnetron, capable of preventing the antenna feeder from being shifted upon tipping off the magnetron.
2. Description of the Prior Art
Referring to FIGS. 1 and 2, there is illustrated a general magnetron used for a microwave oven. As shown in FIG. 1, the magnetron comprises a magnetron body 1, a plurality of radially extending vanes 2 disposed in the interior of the magnetron body 1, inner and outer strap members 3 fitted in upper and lower portions of vanes 2 in an alternate manner and arranged to set the desired frequency of the magnetron, and a filament 5 centrally disposed in the magnetron body 1 and adapted to emit thermal electrons (thermions) which are, in turn, radiated into an interaction space 4.
The magnetron also comprises a magnetic pole 6 disposed above the vanes and an antenna feeder 7 disposed at one side of the magnetic pole 6. The antenna feeder 7 has one end fitted in a selected one of vanes 2 and the other end extending through an output-side seal member 8 and an output-side ceramic member 9 for achieving a hermetic sealing and an insulation to an evacuation tube 10 for evacuating gas out of the interior of magnetron body 1.
With the above-mentioned construction, thermal electrons (thermions) from the filament 5 radiated to the inner and outer strap members in the interaction space 4 are affected by an electrical field exerted between the filament 5 and the vanes 2 and a magnetic field exerted vertically in the interaction space 4 by the magnetic pole 6, to do a cycloidal movement. An electromagnetic wave energy is generated by electrons which are accelerated by the cycloidal movement. The electromagnetic wave energy is transferred to one end of each vane 2 disposed toward the filament 5 and then fed along the vane 2 in the form of current.
Thereafter, the electromagnetic energy is discharged outwardly through the antenna feeder 7 engaged with the vane 2.
On the other hand, the interior of magnetron body 1 should be maintained at a vacuum condition. To this end, an evacuation through the evacuation tube 10 is performed after the antenna feeder 7 is coupled to the vane 2. After the evacuation, the evacuation tube 10 is tipped off.
When the evacuation tube 10 is tipped off, however, the antenna feeder 7 made of a wire material is depressed down and tipped off as shown in FIG. 3, because the antenna feeder 7 extends to the evacuation tube 10 as shown in FIG. 2. Furthermore, such a depression causes the antenna feeder 7 to be downwardly shifted from its initial set position. As a result, the antenna feeder 7 is difficult to be maintained in position on the line path of the output side of magnetron, thereby causing its output characteristic to vary greatly. This is because the output of antenna feeder 7 varies when the output-side construction of magnetron does not maintain a uniform dimension at its portion through which the antenna feeder passes.
As the antenna feeder 7 is downwardly shifted, the vane 2 engaged therewith is also deformed, thereby causing imbalance of overall construction of the magnetron. As a result, the conventional magnetron has fatal defects which degrades the output and the associated characteristics.